まとめ
化石の証拠は,以前は不妊だったレスリアが卵子を産み,初期のサイカドの祖先と結びついていることを明らかにしています. この発見は,サイカドの前身の起源を,ペンシルバニア初期まで遡らせます.
科学分野:
- パレオボタニーは古植物学です.
- 進化生物学の進化生物学について
- 植物形態学 植物形態学
背景:
- Lesleyaは,不妊の化石葉っぱからしか知られていなかった.
- 化石植物の肥沃な構造は,進化の系統を理解するために極めて重要です.
- 以前の解釈では,Phasmatocycasは祖先のサイカド形であると示唆されていました.
研究 の 目的:
- レスレイヤの肥沃な標本について説明します.
- Lesleya,Taeniopteris,およびPhasmatocycasの間の進化的関係を調査するために.
- サイカド前駆体の最古の発生を決定する.
主な方法:
- イリノイ州下ペンシルバニアの化石標本の形態学的分析.
- Lesleyaの肥沃な構造とPhasmatocycasとTaeniopterisの構造を比較する.
- 共有する形態学的特徴に基づく系統遺伝的推論.
主要な成果:
- Lesleyaの標本が発見され,卵子を持つ容器が petioleに付着していた.
- Lesleyaの肥沃な構造は,Phasmatocycasと類似している.
- LesleyaとPhasmatocycasは,Taeniopterisと葉の特徴を共有し,主に静脈の曲線によって異なる.
結論:
- 肥沃な構造を持つレスリアは,TaeniopterisとPhasmatocycasの祖先として提案されています.
- この発見は,現代のサイカッドの先駆者が,約3億2000万年前,ペンシルバニア初期に存在していたことを示唆しています.
- 既知のサイカド先駆者の年齢は,過去約3500万年延長されています.
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